There are many types of cargo which require shipment by a combination of truck and rail, truck and ship, or a combination of all three to reach their designated marketing areas. Most existing methods of handling such products i.e., loading, handling and unloading, are generally inefficient and costly. In addition, they frequently require specialized equipment at points of transfer. In recent years containerized ships have been developed which are adapted to transport dry-bulk or packaged cargo held in specially designed containers. The containers are provided with loading and dumping hatches so they may be filled with a dry-bulk commodity, such as a particulate material, or access doors for filling with boxes, barrels and the like. The containers are then transported by rail or truck to the dockside where they are loaded onto the ship. This does away with the need for special bins or holds in the ship and for elaborate loading and unloading procedures, since the cargo remains in the container and is transported therein until it reaches its ultimate destination.
The transportation of a liquid cargo represents a more complex problem. For large bulk quantities of a liquid, such as oil, special ships or tankers have been designed which also require special loading and unloading facilities. For smaller quantities it is possible to transport a liquid in tanks or canisters. Typically, however, such tanks or canisters have a relatively small capacity and require special handling procedures. Further, the weight of the tanks or canisters relative to that of the liquid contained therein is relatively high with the associated additional shipping expense. Moreover, if the ship to be utilized is containerized and adapted to carry a dry-bulk load in containers, the same ship is not ordinarily suited for liquid loads unless special facilities are provided. Thus, there exists a need for a shipping container for liquids wherein the volume of liquid is not sufficient to warrant a special vessel and transfer facilities, but which is too great for practical shipment in barrels or canisters.
In U.S. Pat. Nos. 4,613,053 and 3,384,106, it is suggested to place a flexible bag in a rigid outer container for shipping a liquid product. A disadvantage of that approach is that the outer box must be specially designed since it must provide substantially all of the lateral support for confining the flexible bag and its liquid contents. In addition, the use of a flexible bag does not prevent wave motion of the liquid contents contained therein during transport. Any wave motion could easily result in a shift in the center of gravity of the container and its contents. The shifting center of gravity could cause an unbalanced condition that might in turn result in damage, particularly if the container was being transported on a truck.